Turbine systems are continuously being modified to increase efficiency and decrease cost. One method for increasing the efficiency of a turbine system includes increasing the operating temperature of the turbine system. To increase the temperature, the turbine system must be constructed of materials which can withstand such temperatures during continued use.
In addition to modifying component materials and coatings, the temperature capability of a turbine component may be increased through the use of cooling microchannels. The cooling microchannels can be incorporated into metals and alloys used in high temperature regions of gas turbines. However, forming an exterior cover over the cooling microchannels can be difficult as thermal spraying directly over the channel can result in coating material filling the channel. One method to prevent the coating material from filling the channel includes filling the channel with a sacrificial material prior to coating, then coating the component and subsequently leeching out the sacrificial material. The filling and removing of the sacrificial material can be both difficult and expensive.
As an alternative to filling and leeching, a thin cover layer can be brazed to the substrate, over the cooling microchannel. However, during the brazing of materials to a surface of the substrate, the brazing temperatures required to sufficiently braze the material may also soften the braze cover material. The softened material can sag or droop into the cooling microchannels, blocking them as they harden. As such, brazing requires a very narrow temperature range, outside of which the component can be damaged or made unusable.
A brazing method that does not suffer from one or more of the above drawbacks would be desirable in the art.